1. Field
Disclosed embodiments relate to a valve train device installed in a cylinder head of an engine, more particularly, to a valve train device including a valve resting mechanism, and also relates to a cylinder head of the engine provided with the valve train device.
2. Related Art
A conventionally known valve train device of an engine of, for example, a vehicle, includes a valve resting mechanism that holds a poppet valve (intake valve and exhaust valve) in a closed position irrespective of an operation of a camshaft of an engine, for example, as disclosed in Japanese Patent Application Laid-Open Publication No. 2000-87711 (Patent Document 1). The valve train device described in Patent Document 1 is mounted to a cylinder head of the engine and configured to transmit power from a camshaft to the poppet valve via a valve tappet. The valve tappet includes a lost motion unit that temporarily interrupts power transmission from the camshaft to the poppet valve.
The lost motion unit is constructed so as to be hydraulically switchable between an interlocking state and a non-interlocking state between the valve tappet and an upper end of a stem portion of the poppet valve. The lost motion unit transmits a vertical motion of the valve tappet in accordance with rotation of the camshaft to the poppet valve, and operates to open or close the poppet valve, for example, during middle speed rotation or high speed rotation of the engine. Furthermore, the lost motion unit temporality interrupts power transmission to the poppet valve irrespective of the vertical motion of the valve tappet, for example, during low speed rotation of the engine, and holds the poppet valve in the closed position.
However, since the valve train device described above includes the lost motion unit between the camshaft and the poppet valve, a size or dimension of the valve train device is increased in a driving direction of the poppet valve, which may result in increase in sizes of components such as a cylinder head and a head cover that house the valve train device, and hence, increasing height of the entire engine. This makes it difficult to ensure an installation space for the engine, and increases weight of the engine, and furthermore, the increase in the size or dimension of the engine further requires production of a dedicated component, which may result in increasing in the production costs.